Tilting jack offshore platform

ABSTRACT

The invention relates to an offshore platform which includes a work deck having a derrick and other ancillary equipment, normally supported above the water&#39;&#39;s surface for drilling and producing an underwater well. The support member includes a plurality of elongated legs or columns which operably connect to the deck. Said legs are flared outwardly in a downward direction to define a broad base of substantially greater dimensions than the deck. The respective legs are anchored at their lower ends to the ocean floor and extend above the work deck. The latter can thereby be adjusted to a desired height above the water&#39;&#39;s surface, stabilized to a desired attitude, or lowered to the water&#39;&#39;s surface. Each leg is registered in a tiltable jack mechanism, which is in turn operably mounted to a mobile carriage whereby the leg upper end can be adjusted by either/or the tilting or longitudinal movement of said jacking mechanism.

United States Patent Inventor lvo C. Pogonowski Houston, Tex.

Appl. No. 836,054

Filed June 24, 1969 Patented July 13, 1971 Assignee Texaco Inc.

New York, N.Y.

TILTING JACK OFFSHORE PLATFORM 5 Claims, 4 Drawing Figs.

US. Cl 6 1/465, 24/263 int. Cl. 1502b 17/00 Field olSearch ...61/46.5,46; 24/263 References Cited UNITED STATES PATENTS 3,008,599 11/1961 Young, Jr. 61/46 X 12/1963 Thornley..... 6l/46.5 3/1965 Roussel 61/465 3,392,534 7/1968 Blenkarn 61/46.5

Primary Examiner-Jacob Shapiro Attorneys-K E. Kavanagh and Thomas H. Whaley ABSTRACT: The invention relates to an offshore platform which includes a work deck having a derrick and other ancillary equipment, normally supported above the water's surface for drilling and producing an underwater well. The support member includes a plurality of elongated legs or columns which operably connect to the deck. Said legs are flared outwardly in a downward direction to define a broad base of sub stantially greater dimensions than the deck. The respective legs are anchored at their lower ends to the ocean floor and extend above the work deck. The latter can thereby be adjusted to a desired height above the waters surface, stabilized to a desired attitude, or lowered to the water's surface. Each leg is registered in a tiltable jack mechanism, which is in turn operably mounted to a mobile carriage whereby the leg upper end can be adjusted by either/or the tilting or longitudinal movement of said jacking mechanism.

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PATENTED JUL 1 3 l9?! TILTING JACK OFFSHORE PLATFORM BACKGROUND OF THE INVENTION In the offshore drilling and exploration for oil, gas and other raw materials, the expedient of a fixedly positioned marine platform is frequently utilized. In such a unit, a working deck is supported at or above the waters surface by one or more rigid members which extend to the floor of the body of water. In the instance of relatively deep waters, it is appreciated that the support members or legs are commensurably long and consequently susceptible to extreme physical strain both in compression and flexure. The leg configuration normally utilized in such platforms might assume any of a number of configurations such as the elongated cylindrical type or an open structured unit. In either instance, the leg is preferably mounted at the working deck in such manner as to be operably engaged by a jacking mechanism whereby the deck can be raised above the water's surface.

In the instance of deepwater offshore locations, the downwardly extending legs are preferably cross braced intermediate the base section and the deck. However, such cross bracing limits base size as well as minimizes the slope and mobility of the leg since it in effect inhibits removal of the support legs from the base pedestal at such time as the platform is to be transported to an alternate water depth. Further, limiting the size of the base reduces the stability and holding power of the platform particularly under stormy weather conditions.

Such offshore platforms are preferably constructed as to be readily disconnected from one drilling site and moved for relocation to another prospective drilling area. It can be appreciated however that due to the normal typography of the ocean floor, the pedestal or base of the platform is not always accommodated on a plane or smooth underwater surface. To the contrary, in most instances the contour of the ocean floor is such as to dispose the pedestal on a tilting angle if the platform were to rest directly on the floor. This circumstance of course affects the platform to the extent that the deck, operably attached to the support columns, has to be adjusted to achieve a desired level condition.

OBJECTS OF THE INVENTION It is therefore one of the objects of the invention to provide a versatile offshore platform adapted for anchoring at a variety of water depths. Another object of the invention is to provide such a platform including means for stabilizing the attitude of the working deck depending from the platform legs. Still another objective is to provide a marine working deck incorporating a plurality of leg clamps which are so arranged to engage one or more floor-imbedded support legs. Still another object is to provide a versatile support leg jack for an offshore platform of the type contemplated, wherein said leg jack is adjustable at the deck level to control the degree of strain imposed on a support leg.

DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric representation of an ofishore platform of the type contemplated including an ocean-floor-mounted base spaced from the deck, and a plurality of intermediate connecting support legs.

FIG. 2 is a view of the platform similar to FIG. 1, illustrating the position of the working deck at the water level and alternately when raised a distance beyond the waters surface.

FIG. 3 is a segmentary view in cross section and on al. enlarged scale taken along line 3-3 in FIG. 1 and,

FIG. 4 is a view taken along line 4-4 in FIG. 3.

DESCRIPTION OF THE INVENTION In overcoming the aforementioned problems, and in achieving the objectives in the invention, there is presently provided an offshore marine platform for fixed positioning in a body of water. The platform includes a working deck which carries a derrick structure together with other equipment essential to a drilling or producing operation at an underwater well site.

The lower end of the platform comprises a pedestal formed of relatively heavy structural members designed to be anchored to the undersea floor at a relatively even disposition. Said pedestal and deck are connected by a plurality of elongated support legs which extend from the pedestal upward to the deck, the leg tops being operably registered in a mobile jack carriage at deck level. The leg jacks are adjustably carried on or within the deck for the purpose of operably altering the working deck to a stabilized position and also for straining the legs in such a manner to minimize the stress induced in the latter as a result of their supporting function.

Referring to FIG. 1, a platform 10 of the type contemplated comprises a relatively planar buoyant deck 11 having an upper surface from which a drilling derrick 12 depends. The latter is connected in the usual manner to a draw works which regulates the derrick hoist for passing drilling tools, casing and equipment through the deck, into the body of water, and subsequently into the ocean floor. While not presently shown such platforms ordinarily incorporate the usual facilities as crews quarters and storage means for the drill pipe and other materials essential to the operation.

A plurality of elongated slots 13 are formed in the deck preferably at the extremities thereof, and extending from upper surface 14 to lower surface 16. Each slot 13 is sufficiently large to accommodate a mobile carriage 17 whereby to pennit horizontal movement of the latter along a plane parallel to the deck surface. Elongated slots 13, to best function with respect to deck 11, are arranged in a radial pattern and directed toward a common focus point preferably at the decks center. Said slots further correspond to the number and positioning of the respective elongated support legs which are registered therein and extend to the sea floor through the prepositioned pedestal.

Each carriage 17 includes a leg registering and holding clamp 18 which is pivotally retained on carriage 17 in a manner such that the upper end of the support leg 19 can be subjected to either horizontal displacement by movement of carriage 17, or to inducement of stress therein due to a tilting displacement of the pivotally mounted leg clamp 18 which incorporates a jacking mechanism.

Platform pedestal 26 is shown in FIG. 1 and 2 as being of a generally triangular configuration and adapted to receive three substantially upstanding support legs 19, 27 and 28. Pedestal 26 is comprised of three corner leg guides 29,31 and 32 having a flared upper opening adapted to slidably receive an elongated leg such as 19 and fastened to the latter by means of a cement or mechanical joint. A series of braces 33 and 34 interconnect the respective corner leg guides one with the other thereby to define a stable, though open structured unit.

The connecting elements between the ocean-floor-mounted pedestal 26, and deck 11, includes the above-noted'closed, cylindrical support legs embodying a generally tubular configuration formed of a series of end-welded steel sections joined one to the other and positioned as shown. However, an alternate leg structure could be utilized such as an open work of welded leg elements.

Referring to FIGS. 3 and 4, each leg 19 is registered within the pivotally mounted upright clamp or leg jack 18. The operation and function of the latter is well known in the art and functionally consists of means for rigidly fixing and supporting an offshore platform by means of a tiltably adjustable clamp. The latter upon actuation grasps a support leg outer surface and in such condition can be actuated to move in a longitudinal direction along the leg.

Each slot 13 of deck section 11 is provided with two pairs of diametrically opposed, although parallel-spaced-apart tracks 36, 37, 38 and 39. One pair 36 and 38 is positioned on the deck upper side, and the other pair 36 and 39 at the underside. The respective tracks are mounted and disposed in a radial direction with respect to deck 11 as to permit horizontal positioning of carriage 17 in a manner to permit the latter to progress along the tracks when a leg is registered in clamp 18.

Referring to NUS. 3 and d, carriage means 117' comprises a vehicle adapted to pivotally support leg jack 118 and to be guidably progressed along the deck-mounted tracks 3%, 317, 38 and 39. Each carriage means comprises in effect substantially identical half-sections spaced on opposite sides of and in supporting relation to leg clamp llill, said halves being jointed into a unitary member by front and rear connections extending therebetween. A pair of hubs dll and 412 are connected to opposite sides of leg clamp 11%, which hubs extend outwardly from the clamp casing and into carriage member 17. In that the respective carriage halves are identical, the following description of one-half will aptly describe the corresponding other half.

A circumferential ring bearing 413 is carried in a circular groove formed on the periphery of hub d2. Said ring bearing 13 is joumaled in a mating member carried on the carriage half whereby the leg jack assembly 113 is rotatably adjusted in a plane normal to the horizontal.

Referring to F116. 6, clamp-tilting mechanism carried on each carriage half includes ring gear or segment 41d mounted to a shoulder 41b extending axially from hub 42. Ring gear 414 is in meshed engagement with a worm gear 4 17, which is in turn longitudinally mounted in thrust bearings at the upper portion of the carriage 117. Rotative movement is transmitted to ring gear M by a shaft connected to and extending axially from the worm gear 437, the latter being further coupled to a transmission and drive means dd such as an electric or air powered motor. Thus, clamping and jacking mechanism l8 can be adjusted as shown in F161. d through either clockwise or counter clockwise rotation about hub as as required in accordance with, or to detennine the position of the leg 119 registered therein.

Carriage 117 is horizontally progressed along the carriage guide tracks by a similar power arrangement. Said arrangement includes a worm gear 211 joumaled within the lower half of carriage 117 and connected to a motor means 419 by a shaft extending from the latter and connected to said worm gear. The lower track 39 is provided with a toothed lateral surface at 511 which normally engages the worm gear 211 whereby rotatable actuation of the latter advances the entire carriage l7 transversely of the deck 11 l a desired distance.

While the transmission and motor means lll and 419 here described with respect to both the carriage tilting mechanism, and carriage progressing mechanism is exemplary, similar mechanisms might be suitably employed in a comparable manner to achieve the desired carriage mobility.

The respective support legs 1'19 are provided with a suitable form of strain-measuring systems such as a plurality of strain gauges 52 and 53 attached at discrete points to the leg outer surfaces. Thus, by assimilating the information derived from all the leg strain gauges, the physical stress imposed on any one leg due to deck weight, wind, or water current loading, might be determined instantly. ln response to such information the respective mobile carriages 117 can be adjusted by movement along the carriage guide means whereby to compensate for excessive leg strain.

Similarly, the tilting mechanism carried on the respective carriages 117 can be actuated in a like manner to adjust a leg upper end whereby to alter the strain pattern induced into the leg by the loading force imposed thereon.

As shown in H6. 2 with the deck llll in the floating position at the water level, the respective carriages 117 are normally at their outermost position with a support leg registered within the respective leg clamps. At such time as the deck is to be raised to an elevated operating position, usually about 50 or 60 feet above the water's surface. the respective leg jacks are operated individually or simultaneously. As the leg jacks are actuated to alternately grip and advance deck lll upwardly along a leg 19, the respective carriages 117 are progressed inwardly whereby to stabilize the platform to compensate for column slope, and to minimize leg strain. At the desired elevated position, the respective leg clamps llli are locked thereby to maintain the deck in a substantially elevated level position, in proper alignment for a drilling operation.

in a normal installation, pedestal section 2'7 is floated to and then lowered to and piled at a desired position at the ocean floor in preparation for a drilling operation. The respective elongated legs 19, 26 and 2% may be prepositioncd in pedestal 26 prior to the latter being submerged or alternately can be inserted subsequent to the pedestal being anchored. As shown in FIGS. 11 and 2, the legs will extend from the leg guide pedestal 26, upwardly through the body of water and terminate at a position above the maximum height to which deck 111 will be elevated.

While the present attitude of the platform as shown in FIG. 2 suggests the pedestal being in a substantially horizontal position with respect to the surface of the ocean floor, such a disposition is not always achievable and more often, the pedestal has to be maintained horizontally by winch lines from the floating deck section until the columns are securely connected to the sea floor and are ready to support the pedestal.

Legs 19, 27 and 28 are thereafter registered within the respective leg clamps 18 carried on the carriage means whereby to permit the positioning of the leg upper end during the raising of the deck above the water's surface.

It will be apparent from the foregoing description that the method is subject to other modifications without departing from the scope of the invention as defined in the following claims.

lclaim:

l. A marine platform for positioning in an offshore body of water including; a buoyant work deck having apparatus thereon for drilling a subterranean well in a substratum beneath said body of water, and having carriage guide means mounted to said work deck,

a pedestal at the platform lower end adapted to be removably fixed to said substratum whereby to anchor said platform,

at least one leg guide carried on said pedestal and including means for engaging a support leg lower end,

at least one elongated support leg received in said leg guide and extending upwardly through said body of water, having the upper end elevated beyond the water's surface,

mobile carriage means operably positioned on said work deck guide means, and being horizontally adjustable thereon,

and said mobile carriage means having leg-gripping means actuatable to removably engage said at least one support leg whereby to adjustably position said carriage means with respect to said at least one support leg's longitudinal axis to regulate induced stresses in said leg.

2. In an apparatus as defined in claim 11 wherein; said carriage guide means on said work deck includes; upper and lower parallel rails being spaced apart to receive said mobile carriage means to permit controlled movement of said carriage means.

3. in an apparatus as defined in claim 2 wherein; said carriage means includes guide-receiving means formed therein and being in registry with said upper and lower rails to be guided by the latter during movement of said carriage.

4i. in an apparatus as defined in claim l wherein; said mobile carriage means includes; motor means engaging said carriage guide means, being actuable to urge said carriage horizontally along said deck.

3. In an apparatus as defined in claim 11 wherein said pedestal includes a plurality of upstanding leg guides being directed inwardly toward the platform center, and an elongated leg received in each of said leg guides being likewise directed inwardly toward the platform center, the upper end of each of said plurality of legs being releasably gripped in said mobile carriage means at said work deck and strain-measuring means carried on each of said plurality of legs, and means for assimilating strain data registered by said strain-measuring means whereby to horizontally regulate the position of said carriage means on said work deck to regulate the strain induced in said plurality of legs. 

1. A marine platform for positioning in an offshore body of water including; a buoyant work deck having apparatus thereon for drilling a subterranean well in a substratum beneath said body of water, and having carriage guide means mounted to said work deck, a pedestal at the platform lower end adapted to be removably fixed to said substratum whereby to anchor said platform, at least one leg guide carried on said pedestal and including means for engaging a support leg lower end, at least one elongated support leg received in said leg guide and extending upwardly through said body of water, having the upper end elevated beyond the water''s surfacE, mobile carriage means operably positioned on said work deck guide means, and being horizontally adjustable thereon, and said mobile carriage means having leg-gripping means actuatable to removably engage said at least one support leg whereby to adjustably position said carriage means with respect to said at least one support leg''s longitudinal axis to regulate induced stresses in said leg.
 2. In an apparatus as defined in claim 1 wherein; said carriage guide means on said work deck includes; upper and lower parallel rails being spaced apart to receive said mobile carriage means to permit controlled movement of said carriage means.
 3. In an apparatus as defined in claim 2 wherein; said carriage means includes guide-receiving means formed therein and being in registry with said upper and lower rails to be guided by the latter during movement of said carriage.
 4. In an apparatus as defined in claim 1 wherein; said mobile carriage means includes; motor means engaging said carriage guide means, being actuable to urge said carriage horizontally along said deck.
 5. In an apparatus as defined in claim 1 wherein said pedestal includes a plurality of upstanding leg guides being directed inwardly toward the platform center, and an elongated leg received in each of said leg guides being likewise directed inwardly toward the platform center, the upper end of each of said plurality of legs being releasably gripped in said mobile carriage means at said work deck and strain-measuring means carried on each of said plurality of legs, and means for assimilating strain data registered by said strain-measuring means whereby to horizontally regulate the position of said carriage means on said work deck to regulate the strain induced in said plurality of legs. 